The present invention relates to power dividers for rf energy, and more particularly to an improved multi-power-level waveguide hybrid coupler.
Hybrid couplers are widely used in microwave circuits for coupling a portion of the electromagnetic energy in one waveguide to another waveguide. In some cases, the coupling ratio is one-half so as to produce an equal split of the power among the two waveguides. In other cases, a smaller amount of the power such as one-quarter or one-tenth of the power may be coupled from one waveguide to the second waveguide. In a common form of coupler, known as a hybrid coupler, the two waveguides are brought contiguous to each other and in parallel relationship so as to share a common wall. An aperture in the common wall provides for the coupling of the electromagnetic energy.
In some applications, it is desirable to have the capability to selectively vary the relative rf power split between the first and second waveguides. One such application is in satellite antenna feed networks, wherein the capability of a variable power split could be employed to vary the radiating power distribution. The power distribution of the satellite antenna system could then be varied by execution of commands from a ground station.
Applicant has previously devised a switchable 3 dB waveguide hybrid which can be switched between the equal-power split state and the state wherein effectively no power is coupled to the second waveguide. This is accomplished by dropping three spaced pins into the aperture in the common wall to effectively close the aperture or by raising the pins to open the aperture to allow coupling of energy into the second waveguide in the conventional manner. For many applications, however, this effective on/off capability is insufficient to achieve a desired system flexibility.
It would therefore represent an advance in the art to provide a switchable waveguide hybrid coupler for providing one of several possible power levels on command and which is relatively simple and inexpensive to fabricate.